The present invention relates to a toy set and in particular, to a toy set having a toy with color memory, and hot and cold-pens, wherein the hot and cold-pens are used to draw an arbitrary image on or mark a temperature-sensitive color changing layer of the toy to cause the image or mark to appear or disappear.
Conventional temperature-sensitive color changing materials include a reversible temperature-sensitive color changing dye. Such materials are used extensively in a wide variety of fields and have a temperature at which the material changes color. The material assumes one of two color states within a room temperature range. That is, the material assumes the other of the two color states only during the period that it is supplied with the heating (or chilling) which is required to cause such state to appear. The material then returns to the one state within the room temperature range as soon as the heating or chilling is terminated and that temperature range is reattained.
A quasi-reversible temperature-sensitive color changing material has been developed which uses the quasi-reversible temperature-sensitive dye disclosed in U.S. Pat. No. 4,720,301 issued Jan. 19, 1988 upon U.S. patent application Ser. No. 807,908, filed Dec. 11, 1985 and assigned to the Pilot Ink Co., Ltd. In response to temperature change, this material exhibits a hysteresis characteristic in which the surface color of the material changes between either colorless and colored states, or between a color (I) and a color (II) in response to a change in temperature, where any of the color or colorless states can be selectively maintained at room temperatures.